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From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	linux-block@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Cc: John Garry <john.garry@huawei.com>,
	Sagi Grimberg <sagi@grimberg.me>, Daniel Wagner <dwagner@suse.de>,
	Wen Xiong <wenxiong@us.ibm.com>
Subject: Re: [PATCH V7 0/3] blk-mq: fix blk_mq_alloc_request_hctx
Date: Fri, 20 Aug 2021 06:38:50 +0800	[thread overview]
Message-ID: <YR7demOSG6MKFVAF@T590> (raw)
In-Reply-To: <20210818144428.896216-1-ming.lei@redhat.com>

On Wed, Aug 18, 2021 at 10:44:25PM +0800, Ming Lei wrote:
> Hi,
> 
> blk_mq_alloc_request_hctx() is used by NVMe fc/rdma/tcp/loop to connect
> io queue. Also the sw ctx is chosen as the 1st online cpu in hctx->cpumask.
> However, all cpus in hctx->cpumask may be offline.
> 
> This usage model isn't well supported by blk-mq which supposes allocator is
> always done on one online CPU in hctx->cpumask. This assumption is
> related with managed irq, which also requires blk-mq to drain inflight
> request in this hctx when the last cpu in hctx->cpumask is going to
> offline.
> 
> However, NVMe fc/rdma/tcp/loop don't use managed irq, so we should allow
> them to ask for request allocation when the specified hctx is inactive
> (all cpus in hctx->cpumask are offline). Fix blk_mq_alloc_request_hctx() by
> allowing to allocate request when all CPUs of this hctx are offline.
> 
> Wen Xiong has verified V4 in her nvmef test.
> 
> V7:
> 	- move blk_mq_hctx_use_managed_irq() into block/blk-mq.c, 3/3

Hello Jens,

NVMe TCP and others have been a bit popular recent days, and the kernel panic
of blk_mq_alloc_request_hctx() has annoyed people for a bit long.

Any chance to pull the three patches in so we can fix them in 5.15?


Thanks,
Ming


      parent reply	other threads:[~2021-08-19 22:39 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 14:44 [PATCH V7 0/3] blk-mq: fix blk_mq_alloc_request_hctx Ming Lei
2021-08-18 14:44 ` [PATCH V7 1/3] genirq: add device_has_managed_msi_irq Ming Lei
2021-10-11 18:23   ` Varad Gautam
2021-08-18 14:44 ` [PATCH V7 2/3] blk-mq: mark if one queue map uses managed irq Ming Lei
2021-08-23 17:17   ` Sagi Grimberg
2021-08-18 14:44 ` [PATCH V7 3/3] blk-mq: don't deactivate hctx if managed irq isn't used Ming Lei
2021-08-23 17:18   ` Sagi Grimberg
2021-09-15 16:14   ` Daniel Wagner
2021-09-16  2:17     ` Ming Lei
2021-09-16  7:42       ` Daniel Wagner
2021-09-16  8:13         ` Ming Lei
2021-10-04 12:25           ` [RFC] nvme-fc: Allow managed IRQs Daniel Wagner
2021-08-19 22:38 ` Ming Lei [this message]

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